Warn developers about deprecated features only once per page-load.

Source/core/page/DeprecationAgent.h

Index: Source/core/page/DeprecationAgent.h
diff --git a/Source/core/page/WindowFocusAllowedIndicator.h b/Source/core/page/DeprecationAgent.h
similarity index 53%
copy from Source/core/page/WindowFocusAllowedIndicator.h
copy to Source/core/page/DeprecationAgent.h
index 86598d7d64fefe8f46fc99ad7d1a1ab99f3467b1..13cd736a780be215a2602dc2676bfaf5593da27f 100644
--- a/Source/core/page/WindowFocusAllowedIndicator.h
+++ b/Source/core/page/DeprecationAgent.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2012 Google, Inc. All rights reserved.
+ * Copyright (C) 2013 Google, Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -23,26 +23,51 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef WindowFocusAllowedIndicator_h
-#define WindowFocusAllowedIndicator_h
+#ifndef DeprecationAgent_h
+#define DeprecationAgent_h
 
+#include <wtf/BitVector.h>
 #include <wtf/Noncopyable.h>
-#include <wtf/RefPtr.h>
+#include <wtf/OwnPtr.h>
 
 namespace WebCore {
 
-class WindowFocusAllowedIndicator {
-    WTF_MAKE_NONCOPYABLE(WindowFocusAllowedIndicator);
+class DOMWindow;
+class Document;
+class PageConsole;
+
+// DeprecationAgent is used to notify developers about the deprecation of APIs
+// they make use of on pages. This notification would generally be the first
+// step towards dropping support for a feature from Blink entirely.
+//
+// To notify developers that a feature they're making use of is deprecated:
+//
+// 1. Add the feature to the Feature enum below.
+// 2. Add a deprecation message to DeprecationAgent.cpp.
+// 3. Call DeprecationAgent::notify(FEATURE_TYPE, "Deprecation message.");
+// 4. There is no step 4.
+
+class DeprecationAgent {

[pfeldman, 2013/04/19 13:04:22]

It is so small that it feels like deprecation could be one of the PageConsole's
responsibilities.

+    WTF_MAKE_NONCOPYABLE(DeprecationAgent);
 public:
-    WindowFocusAllowedIndicator();
-    ~WindowFocusAllowedIndicator();
+    DeprecationAgent();
+    ~DeprecationAgent();
+
+    enum Feature {
+        PrefixedContentSecurityPolicyHeader,
 
-    static bool windowFocusAllowed();
+        // Add new features above this line.
+        NumberOfFeatures, // This enum value must be last.
+    };
+
+    static void notify(Document*, Feature);
 
 private:
-    bool m_previousWindowFocusAllowed;
+    void sendNotification(PageConsole*, Feature feature);
+
+    OwnPtr<BitVector> m_countBits;
 };
 
 } // namespace WebCore
 
-#endif // WindowFocusAllowedIndicator_h
+#endif // DeprecationAgent_h